Implement starts_with, ends_with, and sem_ver custom operators

README.md

@@ -186,6 +186,8 @@ println!("{}", result_str);
 
 ## Custom Operators
 
+This library implements all flagd custom operators for feature flag evaluation. See the [flagd Custom Operations Specification](https://flagd.dev/reference/specifications/custom-operations/) for the full specification.
+
 ### fractional
 
 The `fractional` operator provides consistent hashing for A/B testing and feature flag rollouts. It uses MurmurHash3 to consistently assign the same key to the same bucket.
@@ -217,6 +219,105 @@ The `fractional` operator provides consistent hashing for A/B testing and featur
 - **Deterministic**: Results are reproducible across different invocations
 - **Uniform Distribution**: Keys are evenly distributed across buckets according to weights
 
+### starts_with
+
+The `starts_with` operator checks if a string starts with a specific prefix. The comparison is case-sensitive.
+
+**Syntax:**
+```json
+{"starts_with": [<string_value>, <prefix>]}
+```
+
+**Parameters:**
+- `string_value`: A string or `{"var": "path"}` reference to the value to check
+- `prefix`: A string or `{"var": "path"}` reference to the prefix to search for
+
+**Examples:**
+
+```json
+// Check if email starts with "admin@"
+{"starts_with": [{"var": "email"}, "admin@"]}
+
+// Check if path starts with "/api/"
+{"starts_with": [{"var": "path"}, "/api/"]}
+```
+
+**Properties:**
+- **Case-sensitive**: "Hello" does not start with "hello"
+- **Empty prefix**: An empty prefix always returns true
+
+### ends_with
+
+The `ends_with` operator checks if a string ends with a specific suffix. The comparison is case-sensitive.
+
+**Syntax:**
+```json
+{"ends_with": [<string_value>, <suffix>]}
+```
+
+**Parameters:**
+- `string_value`: A string or `{"var": "path"}` reference to the value to check
+- `suffix`: A string or `{"var": "path"}` reference to the suffix to search for
+
+**Examples:**
+
+```json
+// Check if filename ends with ".pdf"
+{"ends_with": [{"var": "filename"}, ".pdf"]}
+
+// Check if URL ends with ".com"
+{"ends_with": [{"var": "url"}, ".com"]}
+```
+
+**Properties:**
+- **Case-sensitive**: "Hello.PDF" does not end with ".pdf"
+- **Empty suffix**: An empty suffix always returns true
+
+### sem_ver
+
+The `sem_ver` operator compares semantic versions according to the [semver.org](https://semver.org/) specification. It supports all standard comparison operators plus caret (^) and tilde (~) ranges.
+
+**Syntax:**
+```json
+{"sem_ver": [<version>, <operator>, <target_version>]}
+```
+
+**Parameters:**
+- `version`: A version string or `{"var": "path"}` reference
+- `operator`: One of `"="`, `"!="`, `"<"`, `"<="`, `">"`, `">="`, `"^"`, `"~"`
+- `target_version`: The version to compare against
+
+**Operators:**
+| Operator | Description |
+|----------|-------------|
+| `"="` | Equal to |
+| `"!="` | Not equal to |
+| `"<"` | Less than |
+| `"<="` | Less than or equal to |
+| `">"` | Greater than |
+| `">="` | Greater than or equal to |
+| `"^"` | Caret range (allows minor and patch updates) |
+| `"~"` | Tilde range (allows patch updates only) |
+
+**Examples:**
+
+```json
+// Check if version is greater than or equal to 2.0.0
+{"sem_ver": [{"var": "app.version"}, ">=", "2.0.0"]}
+
+// Caret range: ^1.2.3 means >=1.2.3 <2.0.0
+{"sem_ver": [{"var": "version"}, "^", "1.2.3"]}
+
+// Tilde range: ~1.2.3 means >=1.2.3 <1.3.0
+{"sem_ver": [{"var": "version"}, "~", "1.2.3"]}
+```
+
+**Version Handling:**
+- Supports versions with prerelease tags (e.g., "1.0.0-alpha.1")
+- Supports versions with build metadata (e.g., "1.0.0+build.123")
+- Missing minor/patch versions are treated as 0 (e.g., "1.2" = "1.2.0")
+- Prerelease versions have lower precedence than release versions
+
 ## Memory Model & Safety
 
 ### Memory Management